/Engine/Source/Runtime/Engine/Classes/Materials/Material.h
Go through every material, flush the specified types and re-initialize the material's shader maps.
static void UpdateMaterialShaders ( [TArray](API\Runtime\Core\Containers\TArray)< const [FShaderType](API\Runtime\RenderCore\FShaderType) * > & ShaderTypesToFlush, [TArray](API\Runtime\Core\Containers\TArray)< const [FShaderPipelineType](API\Runtime\RenderCore\FShaderPipelineType) * > & ShaderPipelineTypesToFlush, [TArray](API\Runtime\Core\Containers\TArray)< const [FVertexFactoryType](API\Runtime\RenderCore\FVertexFactoryType) * > & VFTypesToFlush, EShaderPlatform ShaderPlatform )